Cooley Spruce Gall Diagnostic Guide

Adelges cooleyi

Cooley spruce gall adelgid, Adelges cooleyi, commonly causes abnormal growths called galls and distortion to the new needles of Colorado spruce and Douglas fir trees. Galls appear as small pineapple shaped growths early in the season. They brown out in the summer and can be confused with seed cones. The galls rarely cause serious harm and can be covered by new growth the following season.

Trees at Risk

Yew

Maple

Holly

Mulberry

Euonymous

Camellia

Signs of Damage

On spruces, pineapple-like formations (galls) are present on the tips of new growth. Galls turn brown during the summer months.

Galls are not formed on Douglas fir, but needles may become discolored, distorted, and prematurely drop from the tree.

Whitney Cranshaw, Colorado State University, Bugwood.org

Whitney Cranshaw, Colorado State University, Bugwood.org

Physical Appearance

Similar to aphids in appearance.

Both winged and wingless adult females are approximately 1 mm long and dark brown to black.

Adults on Douglas fir secrete white strands of wax that cover their bodies.

Petr Kapitola, State Phytosanitary Administration, Bugwood.org

Biology

Cooley spruce gall’s life cycle is fairly complex, as it involves multiple biological forms. Three of these biological forms take place on spruce and two on Douglas fir. The complete life cycle through all five of these forms takes at least two years to complete. The pest’s life cycle can be completed on Douglas fir alone, but the forms that take place on spruce have to find Douglas fir as the second host to complete the entire life cycle.

Treatment Strategy

Cooley spruce gall adelgid can be tough to manage. Once the galls begin to form, contact insecticides usually are ineffective because the insects are protected within galls. Galls can be pruned-out by hand in small trees. If galls are seen during the season, systemic soil application of Xytect™ should be made in late summer/fall because of the early spring activity of adults the following year. Apply Transtect™ in early spring to spruce.

Foliar Spray using Up-Star Gold

A Diagnostic Guide is designed to help you identify a pest issue and management solutions. Always refer to product label for all rates and approved uses. Some images courtesy forestryimages.org. Use of the images does not imply endorsement of treatments by forestryimages.org